The aim of this study is to quantify the synaptic organization of identified basket and stellate cells of the cerebellar cortex. Of special interest is the organization of excitatory vs. inhibitory synapses on proximal vs. distal dendrites and the relative contribution of excitatory synapses made by ascending portion vs. the parallel portion of the granule cell axon. This work requires three-dimensional imaging and reconstruction of large stretches of dendrites from identified neurons and is being performed at the NCMIR using the light and electron microscopes and computer facilities. The synaptic organization of a basket cell in the cerebellar molecular layer has been studied and parts of the cell were reconstructed in 3D. This work has been presented as an abstract at the 1995 Society for Neuroscience meeting. In addition, several stellate cells have been obtained and processed for EM and are currently being reconstructed.